The 2013 Blue
Crab Year

Reports continue to
come in about a very large population of 3 to 4 inch crabs massing on the west
side of the lower Connecticut River – Old Saybrook area.

These crabs have at
times made dock fishing impossible (loss of bait). Reports from trappers also
in some lower river regions and Old Lyme rivers (lower) now report hundreds of
3 to 4 inch crabs while crabbing. As the salt water wedge continues to build
look for these crabs to advance up the river. The tidal wedge is building
strength and excepting any new rainfalls should be in Essex in five days. Blue
crabs did appear on July 4 at Essex only to be pushed south again after heavy
rains. The first sublegal crab I observed was caught in Essex again on July 20th.

These immature crabs
should move up the Connecticut River at night (at least that has been the
pattern) in the next few days.Reports
of 3 to 4 inch crabs have also greatly increased from shore areas Guilford to
Westbrook (Clinton Harbor especially).

No discernable
“wave” movements along the coast however have been detected as of today, July
23rd.

Crabbing Soars in Eastern CT Coves

Crabbing continues
to improve in eastern Connecticut as reports indicate good to excellent catches
in nearly all the coves, including Bakers, Alewife, Jordan, and Masons
Island.Excellent high tide catches from
handliners, low tide night time dippers with flashlights. Still, no reports for
the Pawcatuck River or Thames River: these areas tend to follow the shallow warmer
water Eastern CT coves.

Western Connecticut Crabbers Seek Answers About Habitat
Concerns

Several Western
Connecticut crabbers have asked about signs and symptoms of a habitat failure
for blue crabs. I know of no such research underway at present but two
indicators of a very much changed ecology and habitat would indicate Sapropel
or oatmeal – large new accumulations of organic matter, usually brown leaves as
a dominant source material. Bottom samples may be black underneath this brown
surface layer but the leaf stems remain intact for one to two years (personal
observations) and thick growths mats of sea lettuce (Ulva lactuca) can also be
in close proximity.

What to look for:

1) New thick green
mats of sea lettuce; sea lettuce has been known since the middle 1980s to emit
toxic substances that could kill blue crab Megalops (Johnson and Welsh, 1985)
sometimes in a matter of minutes. Thick mats of decaying sea lettuce mats have
occurred worldwide and once dead, released so much hydrogen sulfide fumes it
overwhelmed beach walkers in Europe.

In France large
amounts of Ulva lactura rotted and emitted large quantities of hydrogen sulfide
gas with tragic results killing school children who had volunteered to help
with cleanup efforts (2009).

China has just
recently experienced a sea lettuce bloom the size of Connecticut!Sea lettuce is now also linked to natural
biocides. When eelgrass populations declined in the 1930s Brant (geese)
switched to eating sea lettuce which led to a report by the US Fish &
Wildlife that hunters complained bitterly that Brant that fed on sea lettuce
tasted terrible. (US Fish & Wildlife
Service, Department of the Interior:Waterfowl Tomorrow US GPO 1964 page
145-146) Brant eventually faced with starvation and on a poor food substitute
Ulva, had to change their migratory routes.

In a 1980s
experiment at the University of Connecticut and a paper published later in the Journal
of Experimental Marine Biology and Ecology details the toxic impacts of Sea
lettuce upon blue crab Megalops in low oxygen conditions. (Detrimental effects
of Ulva lactuca exudates and low oxygen on estuarine crab larvae Journal of
Experimental Marine Biology and Ecology Vol. 90 #1, 1985.)

Blue crab areas
with sudden or much larger sea lettuce populations are now suspected in a
regional western CT blue crab habitat failure.Increases in sea lettuce in good (pre July 2011) crabbing areas have
been reported.

2) Increased
Sapropel and Hydrogen Sulfide gas discharges from leaf rot. Look for previous
harder firm bottoms now soft and filled with rotting leaves, stems, bark and
grasses. When disturbed, these deposits emit a slight sulfur odor (matchstick
smell).If these deposits have putrefied,
than intense hydrogen sulfide (rotten eggs) smells are possible.If areas are low in oxygen bottom organic
matter continues to rot, releasing streams of gas bubbles to the surface. This
is a very bad sign for crab habitat as it shows depleted respiration in low
oxygen conditions. At low tides on hot days with little current, these bubbles
will appear to rise or stream off the bottom.In the summer these bubbles tend to be hydrogen sulfide, in winter and
with greater oxygen in the water, methane.

Several Baldwin
Bridge crabbers over the weekend experienced these conditions briefly, so it’s
just not a Western CT concern, at slack water, low tide, crabbers noticed
bubbles coming to the surface (crabbing was terrible) at this time, perplexed,
I explained it was gas given off by rotting leaves below, and threw a box wing
wall crab trap slowly pulled in to the dock contained about six black oak
leaves in the trap indicating a leafy rotting bottom. When the tide changed and
salt water with more oxygen hit the pier, crabbing quickly improved and bubbles
disappeared.

In the west, look
for these bubbles, at low slack water, their presence could signal a habitat
“failure” for blue crabs.

Every observation
is valuable as we learn more about our blue crab population.

The Search for
Megalops is part of a Project Shellfish/Finfish Student/Citizen Monitoring
Effort Supported by a 2005 grant to The Sound School from the National Fish and
Wildlife Foundation grant #2005-0191-001.

Program reports are
available upon request.

For more
information about New Haven Environmental Monitoring Initiative or for reports
please contact Susan Weber, Sound School Adult Education and Outreach Program
Coordinator at susan.weber@new-haven.k12.ct.us

The Sound School is
a Regional High School Agriculture Science and Technology Center enrolling
students from 23 participating Connecticut communities.